The Army would have upgraded the Apache fleet regardless. They've never been happy to rely on another service for air support, regardless of the quality of that support. That said, of the legacy fighters the A-10 is the only one that would provide unique capability once the F-35 shows up in full force, assuming it lives up to the promises. Makes me wonder what that unique capability could truly be if we invested in a modern RF jamming system.
Having said all that, the long endurance CAS stack right on top of the friendlies isn't survivable in a modern battlefield. Regardless of the fighter dropping the ordnance, we need to invest in the JTAC side of the equation both training and technology.
The other big A-10 mission area (I'm biased, I know) is CSAR, while just about any fighter can do the Sandy 1/2 mission given the training; the Sandy 3/4 mission is a different story. We either need to arm the helos to self escort, which adds weight (always a problem with helos) or shift to another platform that can overfly the low altitude threat. Problem right now is the Osprey can't pressurize, and has no real weapons and is a crappy hover platform. The FVL is 15 years away at the earliest, and the Army is leading it up, so who knows what they'll pick.
We've leveraged the farm on the F-22/F-35 combo, but I think we've sold other missions down the river in the process; at least for the next 15ish years. But I've been known to be wrong on more than one occasion.